Oil well mandrel and stabilizing sleeve assembly

ABSTRACT

An oil well mandrel and stabilizing sleeve assembly that may be inserted as a part of a drill pipe string, with the mandrel and sleeve cooperating to maintain a body of grease under pressure therebetween to protect the engaging threads of the mandrel and sleeve from the abrading action of drilling mud, and to minimize the wear on the threads due to limited relative movement therebetween as the mandrel and sleeve are subjected to longitudinal, rotational and radially directed forces of substantial magnitude during a drilling operation.

United States Patent 1 Rilling OIL WELL MANDREL AND STABILIZING SLEEVE ASSEMBLY Harry L. Rilling, Long Beach, Calif.

Midway Fishing Tool Co., Long Beach, Calif.

Oct. 26, 1971 inventor:

Assignee:

Filed:

Appl. No.:

US. Cl. 175/323, 175/325 int. Cl E2lb 17/042, E21b 17/10 Field oi Search 308/4 A; 175/325,

References Cited UNITED STATES PATENTS 1/1969 Owens 175/323 11/1969 Morris 175/325 7/1936 Kinney 308/4 A 9/1949 Boice 308/4 A X [111 3,747,700 [4 1 July 24, 1973 3,268,274 8/1966 Ortloff et al. 308/4 A 3,318,398 5/1967 3,322,217 5/1967 3,642,079 2/1972 Primary Examiner-David H. Brown Attorney-William C. Babcock [57] ABSTRACT 8 Claims, 6 Drawing Figures OIL WELL MANDREL AND STABILIZING SLEEVE ASSEMBLY BACKGROUND OF THE INVENTION 1. Field of the Invention Oil well mandrel and stabilizing sleeve assemblies.

2. Description of the Prior Art A threaded mandrel in combination with a threaded stabilizing sleeve have been used in the past in a drill string to ream bore holes as well as to maintain the string substantially concentrically positioned within the bore hole. Such prior art devices have suffered from the operational disadvantages that drilling mud is forced between the engaging threads thereof and abrades the same, and the threads tend to wear due to limited relative movement therebetween as the mandrel and sleeve are subjected to substantial forces in a variety of directions during a drilling operation.

The primary purpose in devising the present invention is to provide a mandrel and associated stabilizing sleeve that will be substantially free of the abovedescribed operational disadvantages.

SUMMARY OF THE INVENTION An improved threaded stabilizing sleeve and mandrel for insertion in a drill pipe string. The mandrel has first threads formed on the external surfacethereof that engage second threads formed on the interior of the. sleeve. A circumferential recess is formed on the external surface of the mandrel intermediate the ends of said first threads and sub-divides said threads into upper and lower portions. The recess is in communication with a transverse passage in the sleeve, which passage terminates on its outer end between spaced blades or fins of curved configuration that project outwardly from the sleeve. A first circumferential groove is formed on the external surface of the mandrel above the upper portion of the first threads thereon and a second circumferential groove is formed on the interior surface of the sleeve below the second threads thereon.

First and second resilient sealing rings occupy the first and second grooves and cooperate with the recess and spaces between the first and second threads to define a confined space that is in communication withthe transverse passage. A Zerk fitting or other suitable grease fitting is mounted in the outer end of the trans verse passage. After the mandrel and sleeve have been made up, grease under pressure is discharged into the confined space to completely fill the same. The body of grease in the confined space is substantiallyincompressible. When a drill string having a mandrel and sleeve of the above description included as a part thereof is used, the danger of the first and second threads being abraded by fine particles of the mud is eliminated, for the pressure on the mud is insufficient to compress the confined body of grease to the extent that any mud or foreign material contacts the first or second threads.

During a drilling operation the mandrel and sleeve are subjected to substantial longitudinal, rotational and radially directed forces of substantial magnitude that cause limited relative movement between the first and second threads, and to the extent that they abrade one another even when foreign material is not present therebetween. The confined body of grease in the present invention assures that the first and second threads are at all times fully lubricated, and anywear due to relative movement as above described is minimized From experience it has been'foundthat when a sleeve of the above description isused in a drillingoperation the drillingmud may upon occasion ball upin passing through the elongate curved spaces defined between the fins or blades-on the external surface of the sleeve. By coating the external surface of the sleeve, and particularly the surfaces between the blades or fins, with either an organic or inorganic material havinga low co efficient of friction to the upwardly flowing mud, the above-described tendency of mud to 'ball up may be eliminated.

A majorobjectof the presentin'vention is to provide a stabilizing sleeve and associated mandrel on which it is so mounted that the mandrel an'd'sleeve'cooperate to maintain .a body of grease therebetween under pressure, and the body of greaseserves the dualfunction of preventing foreign material entering ,between the engaging threads of the sleeve and mandrel to abrade the threads, and also maintaining the threads in a fullyslubricated condition to minimize wear thereon as the threads move to a small degree relative toone another due to longitudinal, rotational and radially directed forces that arise from the drilling operation.

BRIEF DESCRIPTION OFTHEDRAWING FIG. 1 is a side elevational view of the mandreland stabilizing sleeve made up and included as a part of a drill string; i y

FIG. 2 is a longitudinal cross-sectional view of the assembly shown in FIG. 1;

FIG. 3 is a fragmentary longitudinalcross-sectional view of the upper threaded portions ,of the mandrel and sleeve;

FIG. 4-is a transverse cross-sectional view of the device taken on the line 4--4of FIG. 2;

FIG. 5 is a fragmentary longitudinal cross-sectional view of the lower portions of the mandrel andsleeve, and

FIG. 6 is a perspective view of an alternate'form of drill pipe stabilizer.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention, as may best be seen in FIGS. 1 and 2, includes an assembly of an elongate mandrel A and stabilizing sleeve B mounted thereon, with the assembly included as a part of a drill pipe string C. The assembly when so mounted reams, wipes and keeps the bore hole (not shown) in which it is disposed smooth and helps to condition the hole before fishing, running log, running casing or the like. The stabilizing sleeve assembly accomplishes the above results automatically as the drilling operation takes place.

Mandrel A and stabilizing sleeve B are of such structure that a body C of grease or other substantially incompressible lubricant is maintained under pressure within the confines thereof, with the body C preventing particled abrasive materialv contacting the engaging threads during the drilling operation, and the body C the top thereof that engage external threads 16 on the lower end of a drill pipe string 18. Mandrel A includes a lower elongate cylindrical portion 20 of smaller diameter than the upper portion 12. A body shoulder 22 is defined at the junction of the upper and lower portions 12 and 20. Lower mandrel portion 20, directly below shoulder 22, has a smooth, first external cylindrical surface 24 in which a transverse circumferential groove 26 is formed. External threads 28 are defined on the exterior surface of the lower mandrel portion 20 below groove 26 and a second smooth cylindrical surface 30 adjacent an externally threaded lower portion 32 of the mandrel. The threaded portion 32 engages internal threads 34 formed on the upper end of a lower drill pipe string 36. The diameter of surface 30 is preferably slightly less than the diameter of the threads 28, which is also true of the first cylindrical surface 24.

After the threads 28 are formed on the mandrel A a circumferentially extending recess 38 is formed on the external surface thereof intermediate the first and second surfaces 24 and 30.

The sleeve B has an external surface on which circumferentially spaced ribs or fins 40 of reverse curvature are formed that define longitudinal grooves 42 therebetween. The interior of sleeve B is defined by upper and lower cylindrical surfaces 44 and 46 of slightly larger diameter than the threads 28. Threads 48 are formed on the interior of sleeve B between surfaces 44 and 46, which threads engage the threads 28 when the sleeve B is mounted on the mandrel A as shown in FIG. 2. A second circumferential groove 50 is formed in the sleeve B and extends outwardly from lower cylindrical surface 46. When the sleeve B is fully threaded on the mandrel A as shown in FIGS. 2 and 3, the upper edge portion 52 of the mandrel is in abutting contact with shoulder 22.

First and second resilient sealing rings 54 and 56 that are of greater width than the thickness of the threads 28 are positioned in first and second grooves 26 and 50 and effect seals with surfaces 44 and 30 as shown in detail in FIGS. 3 and 5. A transverse passage 58 extends through sleeve B, with one end thereof in communication with recess 38 and the outer end of the passage terminating in one of the grooves 42. A grease fitting 60 is mounted on sleeve B in the outer portion of passage 58. Grease C under pressure is discharged through fitting 60 to completely fill the recess 38 and the spaces 62 between the engaging surfaces of the mandrel A and sleeve B. Resilient sealing rings 54 and 56 prevent the flow of grease C in the spaces 62 beyond the positions where the sealing rings effect seals with the surfaces 44 and 30. The grease C under pressure in recess 38 and spaces 62 prevents the entry of mud and fine abrasive particles between the mandrel A and sleeve B, and also assures that the engaging threads 28 and 49 will be fully lubricated to minimize wear thereon as the mandrel and sleeve are subjected to intermittent shocks during a drilling operation.

The external surface of the sleeve B preferably has an I inorganic or organic film 66 covering the same, which film is resistant to the abrasive action of flowing mud and has a low coefficient of friction relative thereto. A film of hard, bright chromium is one example of an inorganic material that may be used for this purpose. Teflon is an example of an organic material that may be used to cover the external surface of the sleeve, and

minimize the tendency of mud (not shown) to ball up as it flows through the grooves 42 between blades 40.

From experience it has been found that when the exterior surface of the stabilizing sleeve B has a film 66 of a ceramic material that is inert and of a high Rockwell hardness deposited thereon, drilling mud does not tend to ball up on the exterior surface of the sleeve as it flows thereby. A material commerically known as Ceramic Application 130, distributed by the Metco Company and having a hardness of 65 Rockwell, is particularly effective as a film 66 on the stabilizing sleeve B.

An alternate form of stabilizer S is shown in FIG. 6 which threadedly engages upper and lower lengths 18' and 36 of a string of drill pipe. The stabilizer S is formed from a heavy cylindrical body 70 of steel that has a bore (not shown) extending longitudinally therethrough, which bore permits the downward circulation of mud from the upper length of drill pipe 18' to the lower length 36'. The upper exterior end of body 70 is provided with threads 14' that are engaged by threads 16 on the lower end of the upper length 18' of drill pipe.

Body 70 has a lower externally threaded portion 32' that engages internal threads 34' formed on the upper part of the lower length of drill pipe 36. The body 70 has a number of circumferentially spaced, longitudinally extending blades 72 of curved configuration on the exterior surface thereof, which blades are separated by spaces 74. The portions of the exterior surface of body 70 and the sides of the blades 72 that cooperate to define the spaces 74 are coated with a film 76 of an inert material that is resistant to the abrasive action of upwardly flowing mud during a drilling operation. The material defining the film 76 must not only be resistant to drilling mud, but must have the physical characteristic that it does not cause the mud to ball up in flowing through the spaces 74 whereby circulation of the mud is lost.

Finely particled titanium dioxide and aluminum oxide has been found to be satisfactory to define films 66 and 76 when applied by a plasma flame or other high temperature means as the films are of a smooth finish, have a high density, have little or no porosity, are firmly bonded to the base material, and resist wetting by aqueous solutions or dispersions.

The stabilizer S is coupled intermediately to lengths of drilling pipe 18' and 36, and when so positioned serves substantially the same functions as the stabilizing sleeve B previously described.

The use and operation of the invention has been described previously in detail and need not be repeated.

lclaim:

l. A two-piece stabilizing tool assembly that may be inserted between upper and lower sections of a drill pipe string, said sections at their adjacent ends having threaded portions, said assembly including;

a. an elongate rigid mandrel through which a longitudinal bore extends, said mandrel having upper and lower portions that define a circumferential body shoulder at their junction, said mandrel having upper and lower threads on said upperand lower portions that engage said threaded portions of said upper and lower drill pipe sections, said lower mandrel portion having longitudinally spaced upper and lower external cylindrical surfaces defined thereon that have threads formed on said mandrel extending therebetween, with a first circumferential groove formed in said first surface, and a circumferential recess in the external portion of said mandrell intermediate said upper and lower cylindrical surfaces;

b. a generally cylindrical stabilizing sleeve having a plurality of spaced longitudinally extending blades on the exterior surface thereof and first and second longitudinally spaced cylindrical surfaces on the interior of said sleeve that have threads defined on said sleeve extending therebetween, with said sleeve, when rotated to place said threads thereon in full engagement with said threads on said mandrell, disposing said first and second cylindrical surfaces in transverse alignment with said upper and lower cylindrical surfaces on said mandrel, a transverse passage in said sleeve that has one end in communication with said recess and the other end situated in a space between said blades, and a second transverse circumferential groove in said second surface that extends outwardly therefrom;

c. first and second resilient sealing rings, said first ring disposed in said first groove and in sealing contact with said first cylindrical surface, and said second ring disposed in said second groove and in sealing contact with said lower cylindrical surface; and d. first means mounted on said sleeve and in communication with said passage for allowing a flowable, substantially incompressible lubricant to be dis charged under pressure into said recess and the spaces between the engaging threads of said mandrel and sleeve between said first and second sealing rings to provide a confined body of said lubricant that prevents drilling mud and abrasive particles flowing to positions between said mandrel and sleeve and which body at all times fully lubricates the engaging threads of said sleeve and mandrel to minimize wear thereon as said mandrel and sleeve are subjected to intermittent shocks during a drilling operation involving said drill string.

2. A tool assembly as defined in claim 1 in which said first means is a grease fitting that permitssaid lubricant to be discharged inwardly through said passage but prevents said lubricant from flowing outwardly therefrom.

3. A tool assembly as defined in claim 1 in which the upper end of said sleeve is in abutting contact with said shoulder when said sleeve is in full threaded engagement with said mandrel.

4. A tool assembly as defined in claim 1 in which the thickness of said sealing rings is greater than the width of the threads on said mandrel. g

5. A tool assembly as defined in claim 1 in which at least the exterior surface portions of said sleeve between said blades is covered with a film of abrasive resistant material that has a low coefficient of friction to drilling mud to prevent said mud balling up as said mud flows through the spaces between said blades.

6. A tool assembly as defined in claim 4 in which said film is an inert ceramic material having a hardness sufficiently high as to be highly resistant to theaction of drilling mud that flows thereby.

7. A tool assembly as defined in claim 4 in which said film has a high density and is composed of a plurality of small particles of high melting point metallic oxides that are fused to one another and tightly bonded to the portion of the surface of said tool assembly with which they are in contact.

8. A tool assembly as defined in claim 7 in which said particles are aluminum oxide and titanium oxide. 

1. A two-piece stabilizing tool assembly that may be inserted between upper and lower sections of a drill pipe string, said sections at their adjacent ends having threaded portions, said assembly including; a. an elongate rigid mandrel through which a longitudinal bore extends, said mandrel having upper and lower portions that define a circumferential body shoulder at their junction, said mandrel having upper and lower threads on said upper and lower portions that engage said threaded portions of said upper and lower drill pipe sections, said lower mandrel portion having longitudinally spaced upper and lower external cylindrical surfaces defined thereon that have threads formed on said mandrel extending therebetween, with a first circumferential groove formed in said first surface, and a circumferential recess in the external portion of said mandrell intermediate said upper and lower cylindrical surfaces; b. a generally cylindrical stabilizing sleeve having a plurality of spaced longitudinally extending blades on the exterior surface thereof and first and second longitudinally spaced cylindrical surfaces on the interior of said sleeve that have threads defined on said sleeve extending therebetween, with said sleeve, when rotated to place said threads thereon in full engagement with said threads on said mandrell, disposing said first and second cylindrical surfaces in transverse alignment with said upper and lower cylindrical surfaces on said mandrel, a transverse passage in said sleeve that has one end in communication with said recess and the other end situated in a space between said blades, and a second transverse circumferential groove in said second surface that extends outwardly therefrom; c. first and second resilient sealing rings, said first ring disposed in said first groove and in sealing contact with said first cylindrical surface, and said second ring disposed in said second groove and in sealing contact with said lower cylindrical surface; and d. first means mounted on said sleeve and in communication with said passage for allowing a flowable, substaNtially incompressible lubricant to be discharged under pressure into said recess and the spaces between the engaging threads of said mandrel and sleeve between said first and second sealing rings to provide a confined body of said lubricant that prevents drilling mud and abrasive particles flowing to positions between said mandrel and sleeve and which body at all times fully lubricates the engaging threads of said sleeve and mandrel to minimize wear thereon as said mandrel and sleeve are subjected to intermittent shocks during a drilling operation involving said drill string.
 2. A tool assembly as defined in claim 1 in which said first means is a grease fitting that permits said lubricant to be discharged inwardly through said passage but prevents said lubricant from flowing outwardly therefrom.
 3. A tool assembly as defined in claim 1 in which the upper end of said sleeve is in abutting contact with said shoulder when said sleeve is in full threaded engagement with said mandrel.
 4. A tool assembly as defined in claim 1 in which the thickness of said sealing rings is greater than the width of the threads on said mandrel.
 5. A tool assembly as defined in claim 1 in which at least the exterior surface portions of said sleeve between said blades is covered with a film of abrasive resistant material that has a low coefficient of friction to drilling mud to prevent said mud balling up as said mud flows through the spaces between said blades.
 6. A tool assembly as defined in claim 4 in which said film is an inert ceramic material having a hardness sufficiently high as to be highly resistant to the action of drilling mud that flows thereby.
 7. A tool assembly as defined in claim 4 in which said film has a high density and is composed of a plurality of small particles of high melting point metallic oxides that are fused to one another and tightly bonded to the portion of the surface of said tool assembly with which they are in contact.
 8. A tool assembly as defined in claim 7 in which said particles are aluminum oxide and titanium oxide. 